The present invention relates to a weed control plate capable of effectively preventing the propagation of weeds germinating at the roots of supports of guardrails or the like.
Guardrails are installed in such places as the boundary between a roadway and a sidewalk, the boundary between a roadway and a road shoulder, the boundary between a road and a slope face, and a median strip in a road. Weeds are likely to grow thick around the guardrails. The reason for this is that the seeds of weeds enter gaps produced around the supports of the guardrails which are driven into the ground even if the sidewalk, the roadway, the slope face and the median strip are paved, not to mention the unpaved ground, and the weeds take root into the gaps.
When cutting the weeds having luxuriated around the roots of the guardrail supports by using an automatic mower, it is necessary to take care not to touch the supports. Therefore, the weed cutting operation is considerably troublesome because of the presence of the obstructive supports. If the rotating cutting blade of the automatic mower touches a support, the cutting blade may break and injure the operator. On the other hand, it takes heavy labor to cut the weeds around the roots of the supports by a manual operation using a sickle or the like.
Under the above-described circumstances, it has heretofore been proposed to install, as shown in FIGS. 9 and 10, a weed control plate 200 or 250 at the root of each support of a guardrail.
More specifically, the weed control plate 200 shown in FIG. 9 has a cylindrical portion 201 and a flange portion 203 provided at the bottom of the cylindrical portion 201. The weed control plate 250 shown in FIG. 10 has a conical shape close to a flat plate. It is deemed that the propagation of weeds around the root of a support 300 can be suppressed to a certain extent by the weed control plate 200 or 250.
However, the conventional weed control plates 200 and 250 suffer from some problems as stated below.
(1) The weed control plate 200 shown in FIG. 9 is vertically split into two separate members to install it on the support 300. The two members of the weed control plate 200 are installed to clamp the support 300 from the right and left sides, and the cut edges of the two members are joined together. In this state, the joint portions are secured by a predetermined securing device, thereby installing the weed control plate 200. PA0 (2) The weed control plate 250 shown in FIG. 10 is cut from the outer periphery to the inner periphery thereof along a single cutting line, and the weed control plate 250 is installed onto the support 300 by opening the cut portion of the plate 250. Thereafter, two edge portions of the plate 250 which are divided by the cutting line are overlaid on one another, and the overlaid portions are nailed on the ground, thereby installing the weed control plate 250. PA0 (3) The conventional weed control plates 200 and 250 are arranged such that the bottom surface of each plate is exactly perpendicular to the direction in which the support 300 stands. Therefore, if the support 300 does not stand perpendicular to the ground, the bottom of the weed control plate 200 or 250 cannot come into close contact with the ground but slopes at an angle to it, resulting in a gap. In such a case, the propagation of weeds cannot effectively be prevented. In a case where the ground is uneven, the bottom of the weed control plate 200 or 250 cannot come into close contact with the ground, resulting in a gap. In such a case also, the propagation of weeds cannot effectively be prevented.
However, the operation of installing the weed control plate 200 on the support 300 by joining together the two members is troublesome because it is necessary to align the two members with each other. In addition, the weed control plate 200 needs to secure the two vertically split members at two joint portions. The presence of two securing portions makes it likely that the clamping force with which the two members clamp the support 300 will weaken with time owing, for example, to expansion and contraction due to solar heat and vibrations caused by the passage of vehicles. If the clamping force weakens, the weed control plate 200 undesirably comes off the ground to become unable to fulfill its purpose.
However, nailing cannot provide very high strength for securing the weed control plate 250 to the ground. Therefore, the weed control plate 250 is likely to separate from the support 300 and fly away in a storm, e.g. a typhoon.
Even in the case of the asphalt ground, not to mention the unpaved ground, the strength with which the weed control plate 250 is secured to the ground by nails may be weakened, for example, by solar heat, vibrations caused by the passage of vehicles, or people's stepping on the plate 250. Accordingly, it is difficult for the weed control plate 250 to continue clamping the support 300 firmly for a long period of time. If the clamping force weakens, the weed control plate 250 undesirably comes off the ground to become unable to fulfill its purpose.
In a case where the weed control plate 250 is formed from a molding resin, the resin plate 250 may be deformed by solar heat. If the weed control plate 250 is deformed, the outer peripheral portion 253 of the weed control plate 250 may be bent to turn upward, and weeds may enter through the bent portion 253.
Although it is conical, the weed control plate 250 has an unfavorably weak strength because the slope angle of the conical surface is exceedingly small. Therefore, the weed control plate 250 may be readily broken if a heavy object, e.g. a vehicle, gets on it.